As a critical piece of equipment ensuring passenger safety, the elevator automatic rescue operating device (ERO)'s core function is to automatically activate and move the car to a level position when the elevator stops operating due to power outages, malfunctions, or other abnormal situations, ensuring the safe evacuation of passengers. However, when the elevator is overloaded, the activation and operation of this device are constrained by multiple factors, requiring comprehensive analysis from the perspectives of overload protection mechanisms, device design logic, and safety regulations.
The elevator overload protection device is a safety system independent of the ERO system. Its function is to prevent danger caused by the elevator exceeding its rated load. When the elevator load exceeds a preset threshold, the overload protection device will be triggered immediately, preventing the elevator from entering operation through methods such as buzzer alarms, displaying overload information on external and internal call screens, and prohibiting the elevator from closing or starting. This mechanism aims to avoid risks such as car and counterweight imbalance, excessive load on the braking system, door opening slippage, or bottoming out caused by overload, thereby protecting the safety of passengers and equipment. Therefore, if an elevator is locked in a stationary state due to overload, the automatic rescue operating device (ERODV) will typically not initiate the rescue process, as overload itself poses a safety hazard, and forcibly moving the car could exacerbate the risk.
The design logic of the elevator ERAV prioritizes safety, and its activation conditions must meet multiple safety constraints. According to national standards, this device only automatically activates when the elevator stops due to reasons other than overload, such as power failure, and must ensure that parameters such as car speed and leveling accuracy meet safety requirements during the rescue process. If the elevator stops due to overload, the device will recognize the overload signal as a "prohibit start" trigger condition, preventing operation when the car and counterweight are unbalanced. For example, when the car load exceeds the rated value, the braking system needs to withstand a greater load. If the ERAV forcibly activates at this time, it may lead to insufficient braking force, causing the car to lose control or slip, resulting in secondary injuries to passengers.
From the perspective of safety regulations and standards, the inspection rules for elevator ERAV explicitly prohibit its activation for rescue operations when electrical safety devices are activated (such as overload protection triggering). This regulation reflects comprehensive protection for passenger safety: on the one hand, under overload conditions, the elevator's mechanical structure (such as wire ropes, guide rails, and brakes) may be at critical load, and forced operation could damage equipment stability; on the other hand, the imbalance between the car and counterweight caused by overload alters the elevator's dynamic characteristics, causing the automatic rescue device's leveling control algorithm to fail, increasing the risk of rescue failure. Therefore, the standard uses technical means to forcibly isolate overload and rescue procedures, ensuring that neither is triggered simultaneously.
In practical applications, the elevator automatic rescue operating device and the overload protection device form a complementary safety barrier. The overload protection device prevents overload risks during normal elevator operation, while the automatic rescue device provides emergency protection in the event of an unexpected elevator stoppage. The two work together through an electrical interlocking mechanism: when the overload protection device is triggered, it sends a prohibition signal to the elevator control system, which is simultaneously received by the automatic rescue device and locks the rescue function; only when the load returns to normal and the overload signal is released can the automatic rescue device return to standby mode. This design avoids accidental rescue activation due to overload, ensuring the safety of rescue operations.
In special scenarios, if an elevator experiences overload and other malfunctions (such as a power outage) simultaneously, the automatic rescue operating device (IRD) still prioritizes overload. For example, if the elevator suddenly loses power while overloaded, the overload protection device will lose power and fail to maintain its alarm state, but the elevator control system will still record the overload fault code. In this case, the IRD will check the fault code before initiating the rescue. If an overload record is found, it will not perform a rescue operation but will instead alert passengers to the overload via audible and visual signals, awaiting manual intervention from maintenance personnel. This design complies with safety regulations and avoids false rescues due to missing information.
The fact that the elevator automatic rescue operating device cannot initiate rescue operations under overload conditions is a crucial component of the elevator safety system. It isolates overload protection and rescue functions through technical means, preventing secondary risks caused by overload and embodying the elevator safety philosophy of "prevention first, safety first." For passengers, adhering to elevator load regulations and avoiding forcibly squeezing into a fully loaded car are key to ensuring their own safety. For maintenance companies, regularly checking the linkage function of overload protection devices and automatic rescue operation devices to ensure their sensitivity and reliability are necessary measures to maintain the safe operation of elevators.
